1. Field of the Invention
The present invention relates to a power source device for a liquid crystal display unit used to display images on an instrument panel of an automobile, a television picture tube, etc., and more particularly to a power source device for a liquid crystal display unit such as a liquid crystal display unit of a dot matrix type, etc. which requires a high driving voltage and which therefore requires a negative power source for the purpose of driving same.
2. Description of the Prior Art
A liquid crystal display unit requires a high driving voltage. An integrated circuit (hereinafter referred to as IC) used in a circuit provided in the signal processing stage prior to the driving voltage stage (the signal processing stage processes the content of the display) is not matched with a power source voltage. In the prior art, when a liquid crystal display unit of this kind is driven, a special IC called a negative power source generating IC 10, as shown in FIG. 4, is used to obtain a negative polarity power source voltage which is applied to a liquid crystal driving IC 11 to effect matching of voltage with that of the liquid crystal display unit 1.
However, in the case where the aforementioned negative power source generating IC 10 is used, and exclusive-use special IC is required, and further circuit parts therefor are also required, thus inevitably increasing the cost. With the recent extensive market need for liquid crystal display units, wherein the number of matrix display units tends to be greatly multistaged, there is a need for higher power negative voltage power sources therefor. The negative voltage capable of being generated by the aforesaid negative voltage generating IC 10 is not enough to cover the aforesaid need, and a few of said ICs 10 need be connected in series, as a consequence of which the device further becomes expensive.